Modern motor vehicles are normally monitored and controlled by an electronic controller. Controllers of this type control the correct functioning of the vehicle and its components and furthermore are able to intervene to correct dangerous situations. In the case of conventional motor vehicles with an internal combustion engine, the controllers are active during operation of the vehicle and, after the vehicle is parked, can be switched off immediately or after a possible short run-on time.
Electric vehicles which can be driven either fully or at least partially (hybrid vehicles) by means of electrical energy from a rechargeable battery (traction battery) are also known. In the case of electric vehicles of this kind, it is generally necessary to connect the rechargeable battery of the vehicle to an energy source and to charge the battery by means of an external connection. A charging system of this kind for charging an energy storage means in a vehicle is known, for example, from DE 10 2010 002 154 A1.
During charging of the traction batteries of the electric vehicle, at least the electronics of the vehicle cannot be fully switched off. By way of example, it is necessary to ensure that the vehicle does not roll away during charging of the traction battery. Otherwise, there is a risk of a charging cable by means of which the vehicle is supplied with electrical energy possibly being ripped off in an uncontrolled manner. In the event of uncontrolled ripping off of this kind in the supply line, there is a risk of an electrical short circuit with far-reaching consequences. In order to preclude this, the possibility of the vehicle rolling away during charging of the traction battery has to be identified and corresponding countermeasures have to be initiated if required. To this end, it is necessary for, in particular, the controller of the vehicle to remain active even during the charging process of the traction battery. Therefore, the controller can collect information from various sensors of the vehicle, evaluate said information and draw conclusions about a possible movement of the vehicle from said information in order to initiate the necessary countermeasures if required.
Since charging of the fraction batteries takes place over a relatively long period of time in the case of electric vehicles, the controller also has to be operated in an active state over this long period of time. In the process, the charging time of the batteries can easily amount to up to five times the actual driving time of the vehicle. This results in a very long operating period of the controller with respect to the overall service life of the vehicle. In order to prevent premature breakdown or failure of the controller, it is therefore necessary to use particularly high-quality components for constructing the controller. Furthermore, particularly complicated tests for ensuring the required quality of controllers of this kind are also necessary. This leads to very high costs for controllers of this kind. Furthermore, the relatively long operation of the controllers during charging of the traction batteries also leads to a correspondingly high level of energy consumption by the controller. Since, in many cases, the controller is fed by a separate low-voltage battery of the vehicle which is not included in the charging process of the traction battery, said low-voltage battery may also be subject to above-average usage.
There is therefore a need for an advantageous monitoring device for a vehicle, which monitoring device has a low probability of breakdown over a long service life and, in the process, can be realized in a cost-effective manner at the same time. There is also a need for a monitoring device for a vehicle, which monitoring device has as low a level of energy consumption as possible.